Set out all measured ingredients on your counter with a large mixing bowl and two smallish saucepans.
Line a square can pan with baking powder and dust with corn flour.
Put the agar agar and water in one of the saucepans and set aside
Place the aquafaba, guar gum and lemon juice in the mixing bowl and, using a hand mixer, beat for around 2 and half minutes until fluffy.
Add the sugar and continue to beat until glossy and full.
Put the maple syrup and vanilla in a saucepan and bring to the boil. Using a candy thermometer, bring the mixture to around 115 - 120 degrees C. Watch carefully. Remove from the heat when temperature is reached.
Turn the hand beater on again and carefully and slowly, pour the maple syrup in to the aquafaba mixture until combined and fluffy.
Put the agar agar and water over the stove top and bring to the boil. As soon as you see a bubble, lift the pan higher above the heat and swirl. Continue to swirl for around 15 - 20 seconds. The mixture will thicken but will not set.
Still swirling, take the pot to the mixing bowl. Start the hand mixer again and, while mixing, pour in the agar agar mixture. Add a pinch of salt and continue to mix until your mixing bowl is cool. This will take around 5 minutes.
Pour the marshmallow in to the prepare cake pan and quickly smooth it out with a lightly greased spoon.
Loosely cover the pan with baking paper and allow to mixture to set for around two hours. I left mine overnight but it will set earlier.
When set, using a knife lightly dusted with cornflour, cut the marshmallow in to serves.
Either dust the squares with more cornflour or toast some desiccated coconut and roll the marshmallows through.